over christmas im borrowing my friends impreza turbo. its a k reg jap import WRX turbo. problem is every time you accelarate hard it cuts out. it drives fine normally but cuts out when you give it some beans? its compleatly random and feels like a rev limiter kicking in. it does it randomly over the rev range. thought it could be petrol as he runs it on 95 unleaded so we tryed 97 super unleaded but still the same. cant get optimax on the isle of wight. when it cuts out it throws you forward in you seat. if you keep your foot on the gas it picks up again. any ideas of obvious things to check on it, looked at all the hoses to see if theres a split but they seem ok. dont know to much about subarus as im a ford man myself. so has anyone got any ideas what could cause it?

 

Sounds like it could be hitting fuel cut to me?

 

Aye sounds like ze fuel cut. I guess buy a Dawes device, and don't boot it 'til you get one. ScoobyECU is the ideal answer but Pavlo is very busy right now.

 

Jap imports are tuned to run on 100 RON not 97 although a WRX might be different.
Running Optimax will certainly help but you wont see any difference until a good few tanks have been swallowed. Optimax has some cleaning chemistry in it which may help clean the crap that has probably accumulated around the valves if you've been using cheap fuel.
Failing that you could use 97 with an Octane Booster like Millers or NF. You should reset the ECU as well.

 

what MY is a k reg...???

If its Pre 96' could be coil packs breaking down...?

 

Sean,

My 98 Sti v3 runs on 95 octane NUL - can't even get SUL where I live I've run it on NUL for the last 4.5 years/40k miles without any problems. Sounds to me more like the old oil vapour in the boost solenoid. Mine had this problem when I bought it - mine was caused by too high an oil level in the sump leading to vapours getting into the boost solenoid. Garage where I bought the car changed the oil before I bought it and filled sump to the 'full' level on the dipstick. Drained some oil from the sump - half way from empty to full is ok, cleaned out boost solenoid and pipes with carb cleaner (other good solvents ok too) and good as new ever since.

Kevin.

 

Second the coil packs. Had the same symptoms myself on my 94 WRX.

Easy to check. Take off the coilpacks bolted on to the top of the spark plugs (12mm bolt). (You will have to remove battery, screenwash bottle and airbox to gain access). Remove rubber insulators off the end of each coilpack and look for hairline cracks in the plastic. If cracked, replace. These will cost you around £75.00 each.

You should ALWAYS use super unleaded or Optimax in an import WRX, preferably with added octane booster. Using normal unleaded is asking for BIG engine trouble.

 

Does sound like fuel-cut to me - think misfiring coilpacks would be a bit more random than that but could be wrong. FFS be careful with that misfire tho if thats what it is - I decided to nail it when mine started misfiring (like I used to do on most n/a cars to 'clear them out') and I blew 3rd out of the gearbox...

 

Why bring up a 4yr old post? Would imagine the problem has been solved now!!